Radio scanning system



Aug. 7, 1945 R. J. MCELHANNQN immo scmmme sygmu Y Filed Aug. 23, 1944"INVENTOR. 1 RAYMOND J.- M ELI-IANPDN.v

[BY I AfroRNEY Patented Aug. 7, 1945 2,380,981 RADIO some SYSTEM RaymondJ. McElhannon, Flushing, N. Y. Application August 23, 1944, Serial No.550,817

(Granted under the act oi March 3, 1883, as

amended April'30, 1928; 370 O. G. 757) 1 Claim.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention pertains to scanning systems for radio waves, fordirecting a radio beam to successive points of an area to be scanned.This invention finds application among others to radio pulse and echodetection systems, commonly termed radar systems.

In accordance with a novel feature of the invention scanning is efiectedby purely electrical means involving no mechanical movements or changein frequency for accomplishing the scan.

The invention employs for operation the velocity modulated type ofoscillator such as the Klystron.

In the annexed drawing the single flgure shows in schematic form apreferred modification of the invention.

Referring to the drawing the rectangle l encloses a velocity modulatedoscillator of special construction comprising a heated cathode foremitting a stream of electrons 2, focused by a tubular focusing element3 maintained negative with respect to the cathode, the electron streampassing thence through accelerator grid 4, maintained at a positivepotential with respect to the cathode for rendering the oscillatoroperative. The focused electron beam passes thence between a pair ofelectrostatic deflecting plates 5 another as shown. The output ofresonant circuit i2 is coupled to dipole 2! over a circuit 23; while theoutput of resonant circuit is is similarly coupled to dipole 22 over acircuit '24. I In the operation of the device, progressive deflection ofthe electron beam between limiting positions I, 8, by action of thedeflecting plates 5 and associated oscillator 6, causes the electronbeam to pass alternately through catcher-grids l4, thence in varyingdegree between both catcher grids l4, l5 and thence only through catchergrids l5, the entire cycle described being thus reversed. This in turncauses radio frequency energy to be radiated first only from dipole 2!to direct the transmitted radio beam in the direction 26; thenceshifting to the position 21 as dipole 22 becomes increasingly energizedwith corresponding decreasing energization of dipole 2| ending in theother limiting direction 28 of the radio beam when only dipole 22 isenergized; whereupon this cycle of operations is repeated T in reverse,and so on.

between which a source of oscillations 6 is conheated for deflecting theelectron beam between limiting positions I, 8 at a desired scanningfrequency. The electron beam passes thence successively between spacedgrids 9, III of a buncher' circuit including a resonant circuit llconnected therebetween. Spaced from the buncher circuit are a pair ofresonant catcher circuits l2, l3, the spaced grids I4 one of which arealigned respectively with the spaced grids I5 of the other. Beyond thecatcher circuits is a collector plate I! maintained positive withrespect to the cathode. For establishing and maintaining sustainedoscillations, feed-back circuits l8, l9 couple the resonant catchercircuits l2, l3 to the buncher circuit H.

20 is a metal parabolic reflector maintained stationary and mountingelf-center a pair of dipoleradiators 2|, 22 inclined at an angle to oneThe circuit may be arranged for reflex Klystron operation by applying asuitable negative potential to plate I1, and omitting the bunchercircuit I l and associated grids 9, Iii in which case circuits l2, l3would operate concurrently as both "buncher" and catcher" elements.

To provide pulse type operation for pulse and echo detection, a keyingcircuit may be interposed4 between the cathode. i and the acceleratorgrid In order to minimize coupling effect between grids I l and I5,circuit l3 may be shifted longitudinally with respect to circuit ii, forexample one wavelength.

I claim:

Apparatus for variably deflecting radio waves, comprising: a velocitymodulated oscillator including a pair of catcher circuits, means'forproducing a velocity modulated cathode beam, and means for variablydeflecting said cathode beam to variably excite said catched circuitsconcur: rently in opposite relation, directive. antenna means energizedby said catcher circuits and arranged to variably direct radiationtherefrom in accordance with said variable energization of said catchercircuits.

RAYMOND J. MOELHANNON.

